178 The N.Z. Journal of Science and Technology. [May 
deputy. None of these men knew that there was only about 1 ft. of solid 
coal between the charge and open place ahead of it. The shot was fired, 
and did not do its work, but blew through into that place ; it made a 
report “ like a cannon ” ; “ the flame came as a ball of fire ” ; “ the place 
was completely full of flame ” ; “ the flame was steady ” ; the light from 
it was sufficient to enable the three men to retreat down the jig from the 
point B on the southern margin of the zone of explosion, where they had 
sheltered unhurt, although the shirt worn by Coppersmith was burned. 
Upon inspection of the zone of explosion it was found that the flame in 
every case had travelled towards the open goaf, fallen to daylight, and to 
the holings to the surface, as shown by arrows on the plan. Along every 
drive marked by such arrows evidence of intense heating was noticeable, 
considerable charring of the coal and of the timber props being visible. 
The flame did not extend throughout the open workings, but propagation 
was confined to the area shown by a stippling of fine dots on the plan. No 
timber was knocked down or falls caused. Nine persons were employed 
in the Deep Creek section at that time ; only one, however, was in the zone 
of flame, and none received any injury. 
On the 17th September the writer inspected the scene of the explosion, 
and found the sides of the pillars slightly damp, in degree insufficient, how¬ 
ever, to moisten a postage-stamp. The floor was wet, although no pools 
were visible ; coal-dust could not be raised by kicking the floor or by 
blowing on the sides. Props were the only timber used ; there were no 
bars to harbour dust. Owing to this small section of workings being 
surrounded by outcrops and holings to daylight, the ventilation was 
excellent and the mine-air as pure as that outside. The writer never saw 
a place more free of coal-dust; but notwithstanding this he is perfectly 
satisfied that sufficient dust was created or raised by the blown-through 
shot to cause propagation, which was confined to a small area owing to 
increased moisture in the unaffected workings. After this occurrence the 
owners of the colliery very wisely introduced British Imperial explosives 
into their collieries at Denniston and Millerton. 
This explosion must be taken as a serious warning, for had it occurred 
in a larger and drier section of the extensive Denniston collieries the loss 
of life might have been appalling. 
In the Regulations under the Coal-mines Act it is provided that— 
128 (2)—In all coal-mines other than opencast workings which are not 
naturally wet throughout no other than a permitted explosive shall be 
used ; and by 129 (/) (iii), In all cases in which permitted explosives are 
required by these regulations, no shot shall be fired unless a shot-firer has 
examined the floor, roof, and sides of all contiguous places within a radius 
of 5 yards of the place where the shot is fired, for coal-dust, and has taken 
efficient steps to render any dust within that area harmless. 
In the case of the Deep Creek section, prior to the explosion it would 
have been a very debatable question as to whether it was not naturally 
wet throughout ; the examination, however, of the contiguous place was 
not made. 
The necessary degree of moisture to render coal-dust uninflammable is 
seldom naturally present in mines. It appears necessary that an additional 
regulation shall be made prohibiting the use of any but permitted explosives 
in all coal-mines except lignite-pits and opencast workings. 
In the report of the U.S. Bureau of Mines, 1916, it is stated that 
investigations have shown that in one case it was found that a mixture 
of 77 per cent, of pulverized Pittsburgh coal and 23 per cent, of water 
(not including the water of composition in the coal) gave a very strong 
